•f  %VJ*p^V;^.: 

»^%H'¥'Sv; 
^^BSdm 

^^v;Vv:  ,  ^ 

^«fc;iS^^ 

BS^HK9| 

%^-S-r^ 


jf  taming  anb  jt'alior. 

LIBRARY 


I  University  "of  Illinois. 


m?; 


1&:.  -g&K 

mT" 


y     r» 


r  *     • 


^-v^wuiiii    uiio    w\ji\.   mi   \ji     UCiUl'T^    tile    ™ 

*     Latest  Date   stamped  below.    A 
i     charge   is  made   on  all  overdue 

b°°kS-            U.  of  I.  Library 

FEE  22  19^ 

i 

FEB    5H 

79 

\j^ 
JAN2S 

v^/vy^ 

1984 

17625-S 

i        *+ . 

t 


FIELD  COLUMBIAN  MUSEUM 

PUBLICATION  7. 
ZOOLOGICAL  SERIES.  VOL.    i,   No.   2. 


ON    CERTAIN    PORTIONS   OF 
THE   SKELETON 


OF 


PROTOSTEGA    GIG  AS. 


BY 


O.   P.   HAY,   PH.  D., 
Assistant  Curator  of  Ichthyology. 

D.  G.  ELLIOT,  F.  R.  S.  E.,  Curator  of   Department. 


CHICAGO,   U.   S.  A. 
November  21,  1895, 


ON   CERTAIN    PORTIONS    OF  THE   SKELETON   OF  PROTOS- 
TEGA  GIGAS  COPE.— O.  P.  HAY. 


The  Dermochelyoid  turtle,  Protostega  gigas,  was  first  described 
by  Professor  E.  D.  Cope  in  Proc.  Amer.  Phil.  Soc.,  1-871,  page  172, 
and  again  in  the  same  publication  in  1872,  page  403.  In  1875,  m  n^s 
''Cretaceous  Vertebrata,"  pp.  99-113,  pis.  IX-XIII,  the  same  writer 
more  fully  described  and  illustrated  the  structure  of  this  remarkable 
reptile. 

The  materials  which  were  in  Professor  Cope's  hands  consisted  of 
a  number  of  vertebrae,  ten  ribs,  some  marginal  bones,  certain  por- 
tions of  the  skull,  some  limb  bones,  and  some  large  plates.  Of  the  lat- 
ter there  were  what  the  describer  regarded  as  two  entire  and  parts 
of  one  or  two  others.  These  plates  he  considered  as  belonging  to  the 
carapace,  and  this  was  supposed  to  be  free  from  the  ribs,  as  the  pecu- 
liar carapace  otDermochelys  is  free  from  the  ribs  of  that  turtle.  In  this 
conclusion  he  was  undoubtedly  wrong,  as  was  later  shown  by  Dr.  G. 
Baur  (Biolog.  Central blatt,  vol.  9,  p.  190).  This  author  pointed  out  that 
the  plates  were  components  of  the  plastron,  an  opinion  that  finds 
abundant  confirmation  in  the  materials  here  to  be  described.  These 
consist  of  a  large  portion  of  the  plastron  of  a  large  individual  whose 
remains  were  entombed  in  the  Cretaceous  deposits  of  Butte  Creek, 
Kansas.  As  shown  in  Plate  IV,  there  are  present  the  hyoplastron 
and  the  hypoplastron  of  the  left  side  almost  complete.  There  are 
also  portions  of  the  same  bones  belonging  to  the  right  side.  These 
parts  of  the  plastron  were  also  accompanied  by  the  nuchal. 

The  length  of  _the  hyoplastron  and  the  hypoplastron  taken  to- 
gether amounts  to  1.2  metres,  including  the  estimated  length  of  a 
piece  missing  from  near  the  hinder  end  of  the  hypoplastron.  These 
two  bones  are  united  by  suture,  which  may  be  seen  immediately  in 
front  of  the  fracture  produced  in  excavating  the  fossil.  The  relation 
of  these  two  bones  is  therefore  unmistakably  indicated.  The  suture 
between  the  two  bones  is  a  very  short  one,  in  comparison  with  that 

of  Thalassochelys. 

67 


58  FIELD  COLUMBIAN  MUSEUM — ZOOLOGY,  VOL.  i. 

The  length  of  the  hyoplastron  is  6icm;  its  width  52.5  cm.  The 
extreme  width  of  the  hypoplastron  is  somewhat  less  than  that  of  the 
hyoplastron,  but  it  cannot  be  accurately  determined.  The  latter 
bone  is  thickest  just  behind  and  somewhat  mesiad  of  the  excavation 
for  the  fore  limb,  and  here  the  thickness  amounts  to  45mm.  The 
hypoplastron  is  not  so  thick,  but  still  quite  thick  and  solid.  The  cor- 
responding bones  in  Professor  Cope's  possession  were  not  more  than 
half  an  inch  in  thickness,  at  the  most.  This  condition  was  in  all 
probability  due  to  the  pressure  to  which  they  had  been  subjected. 

As  will  be  observed,  the  anterior  inner  angle  of  the  hyoplastron 
is  extensively  developed,  surpassing  in  this  respect  that  of  Thalasso- 
chelys, in  which  again  the  plastron  is  more  developed  than  in 
Chelonia.  As  usual  in  all  the  recent  marine  turtles,  this  angle  ex- 
tends further  forward  than  does  the  outer  one.  To  that  border  of 
this  angle  which  lies  next  to  the  fore  limb  was  attached  the  hinder 
end  of  the  epiplastron.  Neither  of  the  epiplastra  was  secured.  In 
Thalassochelys  the  anterior  ends  of  the  epiplastra  extend  in  front  of  a 
line  joining  the  bottoms  of  the  excavations  for  the  fore  limbs  a  dis- 
tance equal  to  that  from  the  bottom  of  the  excavations  for  the  fore 
limbs  to  those  for  the  hind  limbs.  This,  in  the  Protostega  plastron 
before  me,  amounts  to  84  cm.  The  xiphiplastra  of  Thalassochelys 
extend  behind  the  excavations  for  the  hinder  limbs  as  far  as  do  the 
epiplastra  from  the  anterior  excavations.  If  these  proportions  hold 
good  for  Protostega,  the  whole  length  of  the  plastron  would  amount 
to  at  least  2.4  metres. 

As  shown  by  the  figure,  the  hinder  end  of  the  hypoplastron  is 
prolonged  backward  and  somewhat  inward  as  a  long  process.  Mesiad 
of  this  process  there  has  been  another  and,  judging  from  the  example 
of  Chelonia  and  Thalassochelys,  a  longer  process.  A  portion  of  this 
process  is  missing,  but  the  bone,  where  the  fracture  has  occurred  is 
still  21  mm.  thick.  This  missing  process  was  also  evidently  directed 
somewhat  toward  the  middle  line  of  the  body,  as  well  as  backward. 
Between  the  two  processes  has  been  received  the  forked  end  of  the 
xiphiplastron  of  that  side.  The  upper  end  of  the  inner  border  of  the 
outer  process  has  been  chamfered  off  where  it  forms  a  suture  with 
the  xiphiplastron.  This  chamfering  of  the  bone  continues  beyond 
the  point  of  union  of  the  two  processes  and  is  then  carried  backward 
on  the  inner  process  as  far  as  this  remains.  The  upper  side  of  the 
outer  border  of  the  outer  process  has  also  entered  into  sutural  union 
with  the  xiphiplastron.  The  whole  structure  is  here  extremely  simi- 
lar to  that  seen  in  Chelonia  and  Thalassochelys. 


Nov. 2 1, 1895.      SKELETON  OF  Protostega  gigas — HAY.  59 

Had  the  breadth  of  the  body  of  Protostega  possessed  the  same 
ratio  to  the  length  that  we  find  existing  in  Thalassochelys,  the  lower  side 
of  the  animal  would  have  been  about  2.2  metres  wide.  The  positions 
of  the  surfaces  for  union  with  the  epiplastra  and  xiphiplastra,  and  the 
location  of  the  axis  of  strongest  development  of  the  two  plastral  bones 
of  each  side  make  it  evident  that  the  outer  border  of  the  bony  plas- 
tron was  at  a  considerable  distance  from  the  outer  edge  of  the  body. 
This  is  shown  too  by  measuring  outward  from  the  excavation  for  the 
arm  a  distance  proportional  to  that  found  in  Thalassochelys.  The  tips 
of  the  digitations  of  the  plastral  bones  must  have  lacked  as  much  as 
30  cm.  of  reaching  the  marginal  bones.  This  will  leave  a  space  of 
about  120  cm.  from  the  bottom  of  the  excavation  for  one  arm  to  that  for 
the  other.  When  we  come  to  compare  the  distance  from  the  hinder  to 
the  front  excavations,  in  the  restoration  of  Protosphargis  by  Capellini 
(Mem.  Ac.  dei  Lincei,  1884,  3  ser.,  vol.  18),  with  the  distance  of 
the  two  anterior  excavations  apart,  I  find  that  the  two  measure- 
ments have  almost  exactly  the  same  ratio  that  I  have  given  them  in 
Protostega. 

If  we  have  placed  the  plastral  bones  aright,  there  is  left  between 
them  a  great  fontanelle.  Where  the  hyoplastra  are  widest  this  is 
about  43  cm.  in  width ;  and  opposite  the  union  of  the  hyo-  and  hypo- 
plastron,  about  90  cm.  This  is  somewhat  smaller,  however,  than  the 
fontanelle  found  in  Protosphargis,  and  much  smaller  than  that  of 
Dermochelys. 

The  nearest  relative  of  Protostega  is  undoubtedly  Protosphargis  \ 
but  when  we  come  to  compare  the  two  plastra,  we  find  abundant  dif- 
ferences. That  of  Protosphargis  is  considerably  less  developed  than 
that  of  Protostega.  Notwithstanding  this,  there  was  on  the  front  of 
the  hyoplastron  of  Protosphargis  a  long  slender  process  which  ran  for- 
ward and  inward  to  connect  with  the  epiplastron.  In  Protostega  the 
corresponding  angle  of  the  hyoplastron  is  broad,  rounded  off,  and 
digitated.  In  Protosphargis  again  there  is  a  broad  notch  in  the  ante- 
rior and  outer  border  of  the  hypoplastron,  but  none  in  Protostega. 

It  appears  to  be  quite  evident  that  Capellini's  restoration  of  Pro- 
tosphargis is  in  one  respect  not  wholly  accurate.  The  epiplastra  ap- 
pear to  be  too  short  and  to  converge  too  rapidly,  thus  making  the 
plastron  too  short. 

Accompanying  the  plastral  bones  here  described  is  another  bone 
which  must  he  regarded  as  the  nuchal.  Considerable  portions  of  it 
are  wanting  at  each  lateral  extremity ;  and  the  tip  of  the  process  which 
projects  backward  toward  the  first  dorsal  neural  arch  is  also  broken 
away.  The  portion  of  the  bone  remaining  projects  outward  on  each 


60  FIELD  COLUMBIAN  MUSEUM — ZOOLOGY,  VOL.  t. 

side  of  the  middle  line  less  than  18  cm.  If  the  length  of  the  bone  had 
the  same  ratio  to  the  remainder  of  the  carapace  of  Protostega  that  we 
find  in  Chelonia,  it  should  extend  laterally  about  40  cm.  That  it  had 
this  length  so  as  to  reach  the  first  marginal,  is  quite  probable.  If  the 
anterio-posterior  extent  of  the  bone  were  equal  to  that  of  Chclonia,  it 
would  be  about  30  cm.  at  the  narrowest  part;  but  it  is  only  6  cm.  In- 
deed, the  portion  remaining  appears  to  represent  little  more  than  the 
median,  backwardly  projecting  process  and  the  anterior  thickened 
border  of  the  nuchal  of  Chelonia.  The  reduction  in  the  anterio-pos- 
terior direction  really  appears  to  have  gone  further  than  in  Dermochc- 
lys  even.  In  the  latter,  however,  the  anterior  border  of  the  bone  has 
been  removed,  so  that  it,  as  well  as  the  other  borders,  are  jagged 
and  thin.  In  Protostega  it  is  the  hinder  border  of  the  bone  which  has 
been  removed. 

The  anterior  border  of  the  bone  is  relatively  thick,  3  cm.,  and  is 
somewhat  bevelled,  so  as  to  look  downward  and  forward.  On  the 
upper  surface,  near  the  anterior  border  on  each  side,  is  a  broad  shal- 
low groove.  The  process  which  is  seen  to  extend  backward  from  the 
body  of  the  nuchal  probably  reached  the  first  neural.  It  must  then 
have  had  a  length  of  about  28  cm. 

As  in  the  case  of  other  Cretaceous  marine  turtles,  there  is  found 
on  the  under  surface  of  the  nuchal  no  tubercle  for  articulation  with 
the  last  cervical  vertebra. 

As  regards  the  presence  of  a  dermal  carapace  of  mosaic-like 
plates,  such -as  is  found  in  Dermochelys,  the  remains  here  described 
afford  no  light.  No  evidence  of  its  presence  has  been  furnished  by 
any  of  the  specimens  of  Protostega  so  far  produced.  It  is  neverthe- 
less too  early  to  assure  ourselve  that  there  was  no  such  a  structure, 
considering  how  easily  it  could  become  detached  from  a  carcass 
which  was  being  tumbled  about  by  the  waves  and  dragged  by  carni- 
vorous lizards. 

Professor  Cope  has  described  some  of  the  vertebrae  and  ribs  of 
Protostega.  The  vertebras,  like  the  remainder  of  the  skeleton,  had 
been  greatly  flattened  by  pressure,  and  probably  to  this  circumstance 
is  to  be  attributed  their  relatively  great  width.  The  true  relation- 
ships to  the  vertebral  axis  were  thus  rendered  obscure.  Notwith- 
standing the  possession  of  ball  and  socket  articulatory  surfaces,  it  was 
thought  that  some  of  these  vertebras  belonged  to  the  dorsal  region. 
Others  were  regarded  as  appertaining  to  the  neck. 

The  length  of  the  shortest  cervical  vertebra,  the  first  behind  the 
axis,  in  a  specimen  of  Chelonia  with  carapace  790  mm.  long  is  35  mm. 
Professor  Cope's  specimen  of  Protostega  had  apparently  close  to  three 


Nov.2i,i895.      SKELETON  OF  Protostega  gigas — HAY.  61 

times  this  length,  and  we  might  therefore  infer  that  the  shortest  cer- 
vical would  have  a  length  of  about  no  mm.  The  longest  vertebra  in 
his  possession  was  only  60  mm.  long  and  had  at  least  one  plane  sur- 
face. It  is  quite  improbable  therefore  that  it  belonged  to  the  ani- 
mal's neck.  The  longest  neck  vertebra,  the  last  but  one,  of  a  speci- 
men as  large  as  the  one  described  by  Professor  Cope  should  have  a 
length  of  about  142  mm.,  and  the  longest  dorsal  vertebra,  the  third, 
should  have  a  length  of  near  270  mm.  Professor  Cope's  account  of 
the  longest  vertebra  in  his  possesion  makes  it  not  improbable  that  it 
was  the  first  sacral.  The  other  vertebrae  almost  certainly  belonged  to 
the  tail.  Their  size  and  the  form  of  their  articular  surfaces  both 
support  this  interpretation. 

Ten  ribs  were  in  Professor  Cope's  hands.  Each  had  a  proximal 
expansion,  and  it  was  evident  that  these  ribs  did  not  unite  suturally  so 
as  to  form  a  carapace.  But  since  the  dorsal  vertebras  were  regarded 
as  being  so  small,  the  conclusion  was  reached  that  either  the  expanded 
proximal  ends  interfered  with  each  other  in  the  middle  line  or  the 
ribs  must  have  been  articulated  to  diapophyses.  Since,  however,  the 
dorsal  vertebrae  would  have  varied  in  length  from  1 08  to  275  mm., 
and  would  have  been  proportionally  wide,  while  the  widest  rib  de- 
scribed is  140  mm.  at  the  proximal  end,  there  is  no  necessity  for  be- 
lieving that  any  rib  touched  either  its  fellow  or  its  neighbors.  The 
second,  third,  fourth,  and  fifth  vertebras  probably  ranged  from  250 
to  275  mm.,  and  the  next  two  or  three  were  not  much  shorter.  In 
Dermochelys  and  Protosphargis  the  ribs  in  front  of  the  fifth  from  the 
last  are  little,  if  any,  broader  than  this  fifth.  Hence  we  may  safely 
conclude  that  there  were  wide  spaces  between  the  ribs  even  near  the 
vertebral  column.  The  ribs  certainly  lacked  little  of  having  reached 
as  advanced  a  stage  of  reduction  as  they  have  in  Dermoehelys.  Their 
condition  was  probably  much  like  that  seen  in  Capellini's  restoration 
of  Protosphargis. 

Professor  Cope  estimated  that  the  head  of  the  individual  which  he 
described  had  a  length  of  24^6  inches.  However,  basing  my  estimate 
on  the  length  of  the  maxillary  bone  as  figured  on  plate  X  of  "Cretace- 
ous Vertebrata,"  and  making  the  ratio  of  this  maxillary  to  the  length 
of  the  skull  the  same  as  that  found  in  Thalassochelys,  I  can  make  the 
whole  length  of  the  skull,  including  the  supraoccipital  spine,  only 
about  1 8  inches,  or  45  cm.  The  distance  from  the  snout  to  the  con- 
dyle  would  be  close  to  13  inches,  or  32  cm.  Professor  Cope's  specimen, 
judging  from  the  size  of  the  plastral  bones  in  his  possession,  was  not 
much  smaller  than  my  own.  Hence  if  we  estimate  at  32  cm  the  head, 
measured  to  the  condyle,  we  shall  probably  not  make  it  too  great. 


62  FIELD  COLUMBIAN  MUSEUM — ZOOLOGY,  VOL.  i. 

On  the  other  hand,  a  study  of  the  figures  of  the  parts  of  the 
skull  on  plates  X  and  XI  of  the  work  cited  renders  it  highly  probable 
that  the  bone  figured  on  plate  X  as  the  maxillary  is  not  such,  but  the 
postfrontal;  while  the  figure  on  plate  XI,  said  to  represent  the  post- 
frontal,  really  portrays  the  maxillary,  prefrontal,  vomer,  and  pala- 
tine. In  such  case,  the  length  of  the  skull  would  be  about  a  fourth 
greater,  or  40  cm. 

The  length  of  the  carapace  of  Chelonia  has  a  ratio  to  the  plastron 
of  about  31  to  24.  Hence  the  length  of  the  carapace  of  my  specimen 
must  have  been  close  to  3.  i  metres.  The  neck  of  our  living  marine 
turtles  projects  beyond  the  front  of  the  carapace  a  distance  equal  to 
at  least  one-sixth  of  the  length  of  the  carapace.  Hence,  we  are  safe 
in  allowing  50  cm.  for  the  neck  outside  of  the  shell.  We  have  there- 
fore for  the  length  of  this  turtle  the  following  figures : 

Head 32  metres. 

Neck  beyond  carapace 50 

Carapace 3.10 

Total       3.92  metres. 


XM-UMBIAN  V 


ZOOLOGY,  PL.  VII. 


SKULL  OF  CERVUS 7 — FEMALE. 


62  Finn  --;Y,  VOL.  i. 

O  study  of  the  figures  of  the  parts  of  the 

sku'':  renders  it  highly  probable 

th«tt  •  i ,  but  the 

'  the  post- 
,iry,  prefron. 

skull  would  be  al  <urth 

•Ionia  has  a  ratio  to  the  : 
24.     V.  •  >f  the  carapace  of  my 

been  close  to  3.1  metres.  .<  of  our  living  marine 

;.s  beyond  the  front  of  the  carapace  a  distance  equal  to 
At  least  on«?-&uth  of  the  length  of  the  carapace.  Hence,  we  are  safe 
in  allowing  50  cm.  for  the  neck  oui  he  shell.  We  have  there- 

fore for  the  length  of  this  turtle  tl  iigures: 

Head .....  r. ...» ......     .32  me ; 

Neck  beyond  carapace .50 

Carapace 

PLATE  VII. 

Skull  of  Cervus ? — Female. 

Fig.  i.    View  from  above. 

2.  "         "      side. 

3.  "          "      below. 


FIELD    COLUMBIAN    MUSEUM. 


ZOOLOGY,  PL.  VII. 


SKULL  OF  CERVUS ? — FEMALE. 


FIELD   COLUMBIAN    ML- 


ZOOLOGY,   PL.  VIII. 


HEAD  OF  CERVUS  STEERII. — MALE. 


PLATE  VIII. 
Head  of  Cervus  steerii. — Male. 


FIELD   COLUMBIAN    MUSEUM 


ZOOLOGY,   PL.  VIII. 


HEAD  OF  CERVUS  STEERII. — MALE. 


COLUMBIAN    Mv 


•  .JY,  P 


SKULL  OF  CERVUS  STEERII.— MALE. 


PLATE  IX. 

Skull  of  Cervus  steerii.— Male. 

Fig.  i.     View  from  above. 

2.  "         "      side. 

3.  "         "      below. 


FIELD    COLUMBIAN    MUSEUM. 


ZOOLOGY,  PL.  IX. 


SKULL  OF  CERVUS  STEERII. — MALE. 


FIELD   COLUMBIAN    MUSEUM. 


^GV,  PL.  X. 


' 


PLATE  X. 

Skull  of  Cervus  steerii. — Female. 

Fig.  i.    View  from  above. 

2.  "        "      side. 

3.  "        "      below. 


FIELD   COLUMBIAN    MUSEUM. 


ZOOLOGY,  PL.  X. 


SKULL  OF  CERVUS  STEERII. — FEMALE. 


FIELD    COLUMBIAN    MUSEUM, 


ZOOLOG*,  Ki..  XI. 


SKULL  of 


NIGRICANS.—  MALE 


PLATE  XI. 

Skull  of  Tragulus  nigricans. — Male. 
Fig.  i.     View  from  above. 

2.  "         "      side. 

3.  "          "      below. 


FIELD   COLUMBIAN    MUSEUM. 


ZOOLOGY,  PL.  XI. 


SKULL  OF  TRAGULUS  NIGRICANS. — MALE. 


.'OOLOGY,  PL.   XII. 


...       • 

rntni  ^IHBHBBBH 


SKULL  OF  PTEROPUS  AURI-NUCHALIS. — MALE. 


PLATE  XII. 

Skull  of  Pteropus  auri-nuchalis. — Male. 
Fig.  i.    View  from  above. 

2.  "         "      side. 

3.  "         "      below. 

4.  "      of  lower  jaw. 


FIELD    COLUMBIAN    MUSEUM. 


ZOOLOGY,  PL.  XII. 


SKULL  OF  PTEROPUS  AURI-NUCHALIS. — MALE. 


FIELD   COLUMBIAN    Ml 


7OOLCGV,  PC    Xlll. 


:TA  J'4 


PLATE  XIII. 

Skull  of  Pteropus  lucifer. — Male. 

Fig.  i.     View  from  above. 
2.        "         "      side. 
.        "         "      below. 


FIELD    COLUMBIAN    MUSEUM. 


ZOOLOGY,  PL    XIII. 


SKULL  OF  PTEROPUS  LUCIFER. — MALE, 


. 


